It is not so well known that mirages can appear in the sky. To some extent the light from distant objects is always refracted in air if the air is not uniform in density and the light traverses the air at an angle to the planes of the density layers that is less than a right angle. For example, the light from stars below the zenith is bent downwards in proportion to the zenith angle until, at the horizon, the refraction is about half a degree. The rising or setting sun is actually seen about 0.5 degrees higher than it really is.
If there is a strong temperature inversion (where atypically warm air lies over cold air), a similar caustic can form, reflecting light back down and causing inverted images to appear in the sky. This is called a superior mirage and can be seen wherever such an inversion occurs and there is a distant bright source near the horizon (see figure 1).
Unlike the inferior mirage, which is held in position by the hot surface, the air mirage can move, appear and disappear and be magnified by lens effects. Furthermore, some light can penetrate the caustic, be refracted by the thermocline above it and form an upright image of the same object. Consequently, a superior mirage may form two images, one inverted and one upright. Indeed, these two images can merge, losing parts in the process. The resulting image may then not be recognizable. Because of a microscopic (wave-optics) effect called Raman brightening, an interference and focussing phenomenon, mirage images may appear unnaturally bright. They may also shimmer.
warm air ============================================================== ========================.===================================== . ' ' . caustic^ cold air . ' ' . . >' '> . ObserverFig. 1 Light reflected off the caustic in the thermocline of a superior (air) mirage.
There have been few accounts since then. However, in 1979, a resident of Moffat (Scotland) saw and photographed a mirage of Helvellyn, the second highest peak in the Cumberland Mountains, 95 km away (Campbell 1987a). In September 1986 a double superior mirage of a Boeing 757 landing at Edinburgh Airport appeared as a missile flying over a housing estate 6 km away (Campbell 1987b).
'Flying saucers' hit the headlines in 1947 when Kenneth Arnold reported seeing nine bright objects flashing and moving fast near Mt. Ranier in Washington (USA). In fact the objects were superior mirages of nine snow-capped mountain peaks in the Cascade Range. Their 'movement' was only apparent due to movement of his own aircraft. In November 1986, the crew of a Japanese Boeing 747 freighter over Alaska reported being buzzed by a giant UFO; in fact they took avoiding action. But their 'UFO' was a superior mirage of the runway lights of a military airfield 450 km away. A temperature inversion had lifted and magnified the lights so that they looked like rocket exhausts. In December 1980, after seeing a bright fireball over the North Sea (but believing that it was an aircraft falling in flames in the nearby Rendlesham Forest), USAF guards from RAF Woodbridge in Suffolk got permission to search the forest. They returned reporting mysterious lights. The following night the base commander mounted an expedition looking for signs of a landed UFO. He thought he found radioactive traces and evidence of such a landing. He also saw a mysterious blinking light which he followed towards the coast, where he reported other mysterious aerial objects. But the light he saw was from a floating light (lightship), possibly via mirage, and the other objects were planets. Subsequent felling of that area of the forest has convinced UFO buffs that a UFO crashed in the area and that the authorities are concealing the fact (Campbell 1985).
The double mirage of an astronomical object will (normally) show as two lights one above the other. Refraction should place red light at the base and violet light at the top of the upper image, with the colours reversed in the lower image. Various shapes will appear as the two images merge until, in circumstances where only half of each enlarged image is visible, the classic 'flying saucer' will be formed--'two soup plates, one on top of the other with the upper one inverted'. The 'merge line' will sometimes be marked by the appearance of a line of unidentified images (the 'disc' of the 'saucer') in which coloured lights may appear, perhaps as 'windows' (see figure 2), which may appear to rotate.
. . . . half upright image . . --==================-- ' ' ' ' half inverted image ' 'Fig. 2 The classic 'flying saucer'; a merged superior mirage of a star or planet.
Temporal variations in the thermocline may cause changes in shape and/or size during observation and changes in size may be perceived as changes in range. Enlarged and brightened images may be visible in daylight, so accounting for reports of the 'daylight disc'. Because of the more active atmosphere, daylight images are more likely to be mobile. The Trindade Island photographs (January 1958, South Atlantic) appear to show a mirage of Jupiter zooming back and forth across the sky.
Astronomical objects below the horizon can be visible on the horizon via a type of mirage called the Novaya Zemlya effect in which light is repeatedly refracted (ducted) around the Earth for great distances (Lehn/German 1981). This explains the notorious film taken from an aircraft off the coast of New Zealand in December 1978. The source was Venus, then 8 deg. or so below the horizon.
Unfortunately Professor Menzel did not see the application of the mirage hypothesis to many of the cases which he subsequently investigated. Nor did astronomer Dr Allen Hynek, for many years a consultant to the US Air Force and, ultimately, a believer in UFOs. He once asked one of his astronomy students who came from Socorro in New Mexico to find 'an obvious natural explanation' for the notorious CE3 report from a state policeman in Socorro in April 1964. In fact the sighting can easily be explained as a mirage of the star Canopus, then setting in the south over the Rio Grande valley where a temperature inversion seems to have formed. As astronomers, both Menzel and Hynek should have seen that mirages of astronomical objects can explain very many reports.
A panel of scientists, appointed by the (US) National Enquirer to judge the value of UFO reports, awarded the family who reported famous Delphos (Kansas) incident of 1971 a $5000 prize for their report. This case is regarded as a classic and was awarded the newspaper's 'Blue Ribbon' as 'the most scientifically valuable evidence' for the existence of extraterrestrial life reported during the year 1972. In fact the incident appears to have begun with a sighting of a mirage of Saturn.
Few scientists have bothered to investigate UFO reports. They know that UFO reports are a can of worms which can damage their reputations. As a sceptic, Menzel had nothing to fear. Moreover he felt strongly that people should not be misled into believing that aliens were visiting Earth. Hynek, originally a sceptic, succumbed to the view that science cannot explain many 'core' reports and that these represent a new 'unexplained' phenomenon. James McDonald, a meteorologist at the University of Arizona, was a passionate believer in UFOs. But his subsequent suicide may indicate an instability that may have been the cause and not the effect of his interest in the subject. Ufology has attracted several eccentric scientists, those who have already adopted an unconventional view of the world. One such was physicist Harley Rutledge, who believed that UFOs reacted to his thoughts (Rutledge 1981).
Part of the problem is that the solution lies on the border between astronomy and meteorological optics. Modern science is so compartmented that few cross borders, let alone know what lies there. Astronomers are not interested in low altitude astronomy, believing (wrongly) that extinction always precludes observation. Meteorologists are preoccupied with synoptic meteorology and weather forecasting. Atmospheric optical phenomena, including mirages, are of interest to very few. For this reason, the solution to the UFO mystery has remained undiscovered until now. It as fallen to a 'mad' amateur scientist to point out what the professionals could have found many years ago. Even now, professional astronomers dismiss my hypothesis, mainly on the ground that the atmosphere cannot do what I claim it can do.
The only serious scientific study of UFOs was the Condon Report (see Viezee), commissioned by the USAF. Unfortunately its director (Dr Edward Condon) did not take the subject seriously and left co-ordination to a biologist who appears to have prejudged the conclusions. Although the project employed many scientists whose work well describes phenomena that can explain UFO reports (including mirages), its overall conclusions were that UFO reports reveal nothing that could be considered as adding to scientific knowledge and that further extensive study (by the USAF) would not be justified.
Psychologists are well aware that human perception is a hazardous and unreliable process, mainly because perception takes place in the brain, not (where most people think) in the eyes. The brain makes guesses about the external world and builds its picture partly from sampling the input and partly from stored memories. Studies of illusions support this hypothesis, by showing perceptual failures. Philosophers of science now describe perception as 'theory-laden', i.e. what we perceive is a construct of input and theories in the mind about the world. Stimuli are interpreted by the human mind in terms of what it already believes about such stimuli. Consequently we can only identify what we already know.
For everyday purposes, the difference is slight and of no importance. For practical purposes, we can function on guesswork. Problems arise however where the stimulus is anomalous, as in the case of most UFO reports. The human mind abhors uncertainty; it prefers to identify an object as anything rather than not identify it at all. Consequently, faced with an atmospheric mirage which displays unusual, indeed completely unfamiliar characteristics, there will be a tendency to identify it with the only thing the mind has in store that matches. Unfortunately, few of us in the West can claim not to have seen many representations of UFOs on TV, in books and magazines and in films. It is natural therefore that observers will report mirages as UFOs, even with characteristics that were not actually visible but which their minds constructed in order to make sense of the stimulus. If the object cannot be identified as a conventional object, natural or man-made, it is certain to be identified as an alien one, perhaps even with aliens.
Some believe that people who report UFOs are either psychopathological, fantasy prone, hypnotizable or less intelligent than normal. In fact studies have shown that this is not so (Spanos et al 1993). I know of only one case caused by abnormal psychology; the 'witness' suffered a hallucination brought about by his preoccupation with the UFO myth (Campbell 1981). Most people who report UFOs had no prior interest in the subject and were not members of any UFO organization. Nor are professional observers immune to deception. Reports from police officers or pilots are no more reliable than those from anyone else. Until everyone becomes familiar with mirages, they will continue to be reported as UFOs. Physicists, who naively believe that people are objective reporters, make insufficient allowance for perceptual problems and (foolishly) attempt to explain reports as either false or misperceptions of normal objects (which the observers must have been unfamiliar). Many sceptics (especially in the US) make similar hasty judgements and label witnesses as simpletons or frauds. They also jump to the first conventional explanation that comes to mind, refusing to abandon it even when faced with contradictory evidence. Changing the mind of a hardened sceptic is as difficult as persuading a witness that they have seen a mirage.
Where aircraft have not crashed, sights of mirages have caused pilots to undertake dangerous manoeuvres. Lieutenant Gorman, flying a F-51 near Hector Airport (Fargo, N. Dakota) in October 1948, attempted to intercept a mirage of Jupiter for 30 minutes.
Features of those reports which are apparently inconsistent with the mirage hypothesis are likely to be due to the reporter's (and/or the investigator's) ignorance of normal perceptual distortions, false associations and human fear responses. Accounts obtained by hypnosis are certainly unreliable.
It is now evident why UFOs are reported to be a similar appearance all over the world; stars and planets can be seen from anywhere on Earth through an atmosphere which is as likely to produce an inversion in one place as another. Furthermore the few basic shapes reported are consistent with the protean forms seen in mirages, especially the double 'saucer' shape. The 'saucer' disc is not an imagined shape for alien space craft (after all our spacecraft are a completely different shape). It is a real shape seen in the sky.
It is now evident why UFOs are reported to move about the sky at great speed and execute 'impossible' manoeuvres; there are no limitations on the speed or manoeuvres of an image. The hypothesis also explains why UFOs are so often reported to be silent, even while executing manoeuvres which should cause sonic booms or thunderclaps. They are not real craft.
The mirage hypothesis accounts not only for the foo-fighters of the Second World War and the Korean War, but the mystery airships reported in the USA in the 1890s. I predict that this powerful hypothesis will find universal application and solve countless cases. It may even explain reports of other strange phenomena such as ball lightning, will-o'-the-wisp or appearances of the Virgin Mary.
Huddart, Joseph (1797): Observations on horizontal refractions which affect the appearance of terrestrial objects and the dip, or depression of the horizon of the sea, Phil. Trans (R. Soc. Lon.) 87, pp 29-42.
Lehn, Waldemar H and B A German (1981): Novaya Zemlya effect: analysis of an observation, Applied Optics, 20(12)2043.
Menzel, Donald H (1953): Flying Saucers, London.
--------- and Lyle G Boyd (1963): The World of Flying Saucers, New York.
--------- and Ernest Taves (1977): The UFO Enigma, Garden City.
Rutledge, Harley (1981): Project Identification, Englewood Cliffs.
Spanos, Nicholas P et al (1993): Close Encounters: An Examination of UFO Experiences, J. Abnormal Psychology, 102(4)624-32.
Viezee, William (1969): Optical Mirage (Ch. 4), Scientific Study of Unidentified Flying Objects (The Condon Report, ed. Daniel S Gillmor), London. Part of chapter written by Gordon Thayer.
Vince, Samuel (1799): Observations upon an unusual horizontal refraction of air..., Phil. Trans. (R. Soc. Lon.) Part 1, pp. 13-23.
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